While popular media coverage of people following a Primal way of eating tends to paint us as carnivorous meat enthusiasts gorging on steaks, bacon, bun-less hotdogs, and little else without regard for quality, in truth we are far more discerning about our choices of meat. We prefer pastured pork[7] and poultry[8], grass-fed and finished beef[9], lamb, and bison, and generally deplore the conditions of concentrated animal feeding operations[10] (CAFOs). And many of us actively limit processed meat – sausages, bologna, lunch meats, bacon, and the like. You’ll often catch us coming down quite hard on processed meat altogether, making a point to distinguish between its health effects and those of unprocessed meat when responding to studies that lump the two together as “meat.”

And as much as we reiterate that observational studies cannot establish causation, processed meat consumption is consistently linked to poor health outcomes. Now, it could very well be that processed meat consumers tend to do other unhealthy things, like not exercise, sleep poorly, eat other processed foods, eat buns with their hot dogs and pizza dough with their pepperoni. Researchers usually try to control for at least some of those variables, but it’s impossible to cover every unhealthy aspect of a person who simply doesn’t care about their health. You can’t quantify everything. That likely explains much of the relationship between processed meat and poor health outcomes.

But let’s assume for a second that the observational studies do show causative relationships. What could be causing it?

Nitrosamines

Nitrosamines are carcinogenic compounds. In animal studies, they’re used to reliably give rodent subjects cancer[11]. In observational studies, they’re linked to human cancers[12]. Nitrosamines form when nitrites (a common preservative in processed meats) bond with amino acids (also found in meats); this can occur during the processing of the meat or in the stomachs of those who eat it. Since processed meats contain both nitrites and amino acids, it’s kind of a perfect storm. Case closed?

Not quite. Another excellent source of nitrates (which convert to nitrites in the body) are most of the vegetables we eat, particularly the green ones. In fact, the majority of the nitrates we consume come from vegetables[13] – not bacon or hot dogs or head cheese (well, maybe except for that German kid I went to grade school with who ate nothing but thick slices of head cheese in between rye bread every day for lunch). Plus, the majority of the nitrosamines we’re exposed to come from endogenous formation in our stomachs[14], not from dietary pre-formed nitrosamines. And endogenous nitrosamine formation can occur without any processed meat at all. A meal of fish (amino acids) and greens (nitrates which commensal oral bacteria convert to nitrite), for example, could conceivably increase nitrosamine formation, but I don’t think that means fish and greens are unhealthy.

Poor Quality Animals

Your average salty slab of beige pseudo-meat doesn’t come from a pastured animal. Obviously. Those Oscar Mayer wieners quivering in the dusky summer light of a million American backyard barbecues? Every bite contains bits and pieces from hundreds of individual animals who never knew what it was like to walk on grass. Even in countries like Italy, whose traditionally-cured meats are famous the world over, industrial farming is replacing smaller, more intimate farming[16]. It doesn’t matter how many traditional Mediterranean arm hairs you find in your guanciale. Unless the package mentions it, or the producer confirms it, the majority of processed meat is made from CAFO cows, pigs, and poultry who ate corn (and its oil) and soy (and its oil) centric diets and have imbalanced fatty acid ratios (more omega-6 PUFA, less saturated/monounsaturated/omega-3[17] PUFA). That isn’t to say that it’s terrible for you, or that you can’t mitigate the imbalance by consuming more omega-3s, but it is to say that when you eat processed meats, you’re more often than not not eating the best quality meat you can get your hands on.

Oxidized Lipids (Cholesterol and Fatty Acids)

We all know about the formation of oxidized cholesterol and oxidized fatty acids in foods cooked at high temperatures, and we all know why we should limit these whenever possible: they can be incorporated into our serum cholesterol, increasing its oxidative instability and our oxidative stress, and eventually leading to atherosclerosis[18]. During processing, many processed meats are cooked at temperatures high enough to oxidize the lipids before they even reach your local grocery store. Things like precooked breakfast sausages, hot dogs, and Vienna sausages qualify (PDF[19]). Processed meats like mortadella (which is baked at a low heat) and salami (which is cured but not cooked), however, are relatively free of oxidized lipids[20]. As a general rule, the higher the polyunsaturated fat content of the meat (CAFO-fed pork and poultry are especially high in PUFA), the greater the potential for oxidized fats. Sure, overcooking fresh, unprocessed meat can oxidize the lipids, too, but you’re starting from scratch. The problem with precooked processed meats is that you’re starting from behind.

A Skewed Potassium/Sodium Ratio

With a diet based on unprocessed meat, the ratio is far easier to monitor and optimize. You control the flow of salt, adding as much or as little as you want. Fresh meat itself also has a favorable potassium/sodium ratio, and the rarer you eat your meat, the more potassium-rich juices you’ll consume.

With a diet based on processed meat, a favorable ratio is difficult to maintain. For one, many processed meats arrive pre-cooked and/or with all (potassium-rich) moisture removed, which removes or destroys much of the potassium. And two, most processed meats come heavily salted, further throwing off the ratio.

Heterocyclic Amines

When meat is directly exposed to high temperature, the amino acids, sugars, and creatine within it react to form heterocyclic amines (HCA), which are mutagenic in animal studies and linked to cancer of the prostate[22], pancreas[23], and colon[24] in observational studies. Certain processed meats can have signficant amounts of HCAs[25], with well-done (almost burnt) bacon and sausage showing more than hot dogs, deli meat, and pepperoni, but fresh meats exposed to high heat cooking (like rotisserie chicken skin[26]) usually have more.

And so it’s a mix of real problems and overblown threats. As you can probably see, not all of these problems are inherent to processed meat and many of them can be countered with proper precautions:

Treat cured meats as condiments that enhance your vegetable and fresh meat dishes, not main courses. This will allow you to use and afford high-quality cuts with better nutrient and fatty acid profiles, since you aren’t blowing through them so quickly and they’ll last longer. This will also dampen the potential health impact of poorer quality cuts if you go that route, since you’re not eating so much in one sitting.

So, how much processed meat should you be eating? Eh, hard to say. A little bacon[29] with your eggs here (okay, a lot), maybe some charcuterie there as an appetizer before a dinner party, some diced pancetta with Brussels sprouts – this is pretty typical among the crowd that reads this blog. I strongly advise against basing your diet on pepperoni, bacon, and hot dogs – even high-quality ones using grass-fed and pastured animals – but I think that goes without saying. In the end, the majority of Primal eaters are not basing their meals on processed meat.